Push-to-talk (PTT) is a two-way communication service that works like a walkie-talkie. A normal cell phone call is full-duplex, meaning both parties can hear each other at the same time. PTT is half-duplex, meaning communication can only travel in one direction at any given moment. A token-based model of operation, in which a person must be first granted access to the floor by a floor control mechanism before he may speak to other session participants, typically governs most PTT sessions. For instance, a PTT-enabled handset typically requires that a caller press and hold a button while talking, and then release the button when they are done. Any listener may then press their button in a similar manner to request access to the floor in order to respond.
PTT applications have been utilized in the radio and microwave communication industries for many years. A variety of different applications are ubiquitous today. For example, dispatch services such as police and fire departments, paramedic units, and security teams routinely use PTT applications for field communications. More recently, mobile service providers have begun to provide enhanced PTT services based on Internet Protocol (IP) based solutions. For instance, push-to-talk over cellular (PoC) applications are actively being pursued by mobile service providers in the Open Mobile Alliance (OMA) standards body for use in chatting with families, buddies and in certain business applications, such as dispatch services, security services and various government agencies (e.g., fire, ambulance, police, FEMA, etc.). The OMA PoC approach is based on the session initiation protocol (SIP), a widely-used signalling protocol for voice over IP (VoIP) communications in which transfer of packets is done using the real-time transport protocol (RTP). RTP is a known protocol for transmitting real-time data such as audio or video streams. The RTP control protocol (RTCP) is an associated protocol useful for maintaining RTP session quality. The talk burst control protocol (TBCP) is a known protocol that uses extension features of RTCP to invoke floor control within a PoC environment.
By way of further background, a system and method for controlling the transmission of talk bursts using a talk burst control protocol is described in U.S. Patent Publication No. 2006/0034336. A system for providing media services in voice over IP (VoIP) telephony in which audio is transmitted in packet streams such as RTP/RTCP packets is disclosed in U.S. Pat. No. 6,947,417. U.S. Pat. No. 6,044,081 teaches a communications system and multimedia system that allows private network signaling to be routed over a packet network.
One of the problems with providing enhanced PTT services is that many legacy communication systems that accommodate PTT based radio communication devices are often incompatible with each other. This can make it difficult to integrate different PTT services in situations where endpoint communication devices must share the same logical floor and arbitrate across different applications. Many times, with disparate applications there arises a need to provide different floor control characteristics applicable to these different application scenarios.